Melanin ˈmɛlənɪn (
μέλας -
melas, "black") is an
ubiquitous natural
pigment found in most organisms (
spiders are one of the few groups in which it has not been detected). In animals melanin pigments are derivatives of the amino acid
tyrosine. The most common
biological melanin is
eumelanin. This is a brown-black
polymer of dihydroxy
indole carboxylic acids and their reduced forms. Another common form of melanin is
pheomelanin, a cysteine-containing red-brown
polymer of
benzothiazine units largely responsible for red hair and
freckles.
The production of melanin in human skin is called
melanogenesis. Production of melanin is induced by UVB-radiation simulated by DNA, which is also a photoprotectant. This occurs by means of a process called "ultrafast
internal conversion". This property enables melanin to dissipate more than 99.9% of the absorbed UV radiation as heat (see
photoprotection). This prevents the
UVB radiation damage that is responsible for the formation of malignant melanoma and other skin cancers.